What am I looking at?

In spite of my severe obsessive-compulsive tendencies when it comes to germs, I rolled up my sleeves yesterday and dismantled the 1973 Kilgore toilet in my downstairs bathroom -- something in the tank was running non-stop just recently, and after my husband and I replaced a few parts and made adjustments in the tank to try to stop it, we made the decision to put money toward replacing the toilet altogether instead of calling a plumber out for further diagnosis. Husband performed the final lift into my obsessively-outlaid contractor trashbag setup so that I could scoot things out to discard. Here's what we found below the toilet:

What am I looking at? It sure doesn't look as straightforward as on YouTube
Evidently, there's a leak. Blown wax seal? The toilet had been caulked all around the edges since we moved in, unfortunately, so I'm not sure when the leaking started. I see part of the flange, covered in waste and maybe corroded?
Before I don a hazmat suit to handle cleaning things up to see if the flange itself merits replacement, should I also worry about the subfloor since there's been leakage?
Is it time to call out the (non-Rooter) pros?

Thanks in advance!
And, THANKS to everyone who's contributed great stuff to this forum. Picked out a Toto Drake as the replacement after much agonizing over our 11" rough-in.

Hard to tell from the picture, but that just looks like a wax ring or two smushed (as it should be) under the toilet. Looks like a little remaining plastic funnel-ish thing from the wax ring as well.

No need for a hazmat suit. Get a decent pair of rubber dish gloves and a putty scraper and just scrape away the wax and schmutz, careful not to knock it down your drain hole (put a rag in there if you haven't already to block the gas and your scrapings). Once you clean that all up, you should see the flange. Remove the old closet bolts and try to get a decent set, preferably one that has two nuts and two washers per bolt. Then you first attach the bolt to the flange, then your wax, then mount the toilet and use the other nut and washer to secure the toilet to the flange. (Most people just use one nut and washer to secure the whole thing, but many pros use the double-nut technique, which is superior. Terry sells a good set of closet bolts in his toilet installation kit; you can use that for guidance (or purchase).)

When you install your new Drake, if that flange top is below the finished floor, then you will need two wax rings, one with a plastic funnel/flange and one without. Put the one without the plastic on the floor first, then put the one with the plastic on top of that, then put the toilet bowl down on top of that. Most of this is in Jamie's instructions on how to install a Drake, which is at the top of this section of the forum.

Good luck. Let us know how it goes. It looks nasty but I think it's really typical, unless there's something I don't see in the photo. In short, clean it up and see what you have.